diff --git a/src/RealMeService.php b/src/RealMeService.php
index 54178d6..c874625 100644
--- a/src/RealMeService.php
+++ b/src/RealMeService.php
@@ -18,12 +18,15 @@
 use SilverStripe\Core\Environment;
 use SilverStripe\Core\Injector\Injectable;
 use SilverStripe\Core\Injector\Injector;
+use SilverStripe\Core\Validation\ConstraintValidator;
 use SilverStripe\RealMe\Exception as RealMeException;
 use SilverStripe\RealMe\Model\FederatedIdentity;
 use SilverStripe\RealMe\Model\User;
 use SilverStripe\Security\Member;
 use SilverStripe\Security\Security;
 use SilverStripe\View\TemplateGlobalProvider;
+use Symfony\Component\Validator\Constraints\NotBlank;
+use Symfony\Component\Validator\Constraints\Url;
 
 class RealMeService implements TemplateGlobalProvider
 {
@@ -458,11 +461,11 @@ public function enforceLogin(HTTPRequest $request, $backUrl = null)
         }
 
         $backUrl = $this->validSiteURL($backUrl);
-        
+
         if (!$backUrl) {
             $backUrl = Director::absoluteBaseURL();
         }
-        
+
         // If not, attempt to retrieve authentication data from OneLogin (in case this is called during SAML assertion)
         try {
             if (!$session->get("RealMeErrorBackURL") && Controller::has_curr()) {
@@ -800,7 +803,7 @@ public function getAssertionConsumerServiceUrlForEnvironment($env)
         }
 
         $domain = $this->getMetadataAssertionServiceDomainForEnvironment($env);
-        if (filter_var($domain, FILTER_VALIDATE_URL) === false) {
+        if (!ConstraintValidator::validate($domain, [new Url(), new NotBlank()])->isValid()) {
             return null;
         }
 
diff --git a/src/Task/RealMeSetupTask.php b/src/Task/RealMeSetupTask.php
index b7d2c1f..dd2c3c1 100644
--- a/src/Task/RealMeSetupTask.php
+++ b/src/Task/RealMeSetupTask.php
@@ -10,8 +10,11 @@
 use SilverStripe\RealMe\RealMeService;
 use SilverStripe\Control\Director;
 use SilverStripe\Control\Controller;
+use SilverStripe\Core\Validation\ConstraintValidator;
 use SilverStripe\Dev\BuildTask;
 use SilverStripe\Dev\Deprecation;
+use Symfony\Component\Validator\Constraints\NotBlank;
+use Symfony\Component\Validator\Constraints\Url;
 
 /**
  * Class RealMeSetupTask
@@ -276,45 +279,33 @@ private function validateEntityID($forEnv)
             );
         }
 
-        // make sure the entityID is a valid URL
-        $entityId = filter_var($entityId, FILTER_VALIDATE_URL);
-        if ($entityId === false) {
-            $this->errors[] = _t(
-                RealMeSetupTask::class . '.ERR_CONFIG_ENTITYID',
-                'The Entity ID (\'{entityId}\') must be https, not be \'localhost\', and must contain a valid ' .
-                    'service name and privacy realm e.g. https://my-realme-integration.govt.nz/p-realm/s-name',
-                array(
-                    'entityId' => $entityId
-                )
-            );
-
+        $validationMessage = _t(
+            RealMeSetupTask::class . '.ERR_CONFIG_ENTITYID',
+            'The Entity ID (\'{entityId}\') must be https, not be \'localhost\', and must contain a valid ' .
+                'service name and privacy realm e.g. https://my-realme-integration.govt.nz/p-realm/s-name',
+            ['entityId' => $entityId]
+        );
+        // make sure the entityID is a valid URL with HTTPS protocol
+        if (!ConstraintValidator::validate($entityId, [new Url(protocols: ['https']), new NotBlank()])->isValid()) {
+            $this->errors[] = $validationMessage;
             // invalid entity id, no point continuing.
             return;
         }
 
-        // check it's not localhost and HTTPS. and make sure we have a host / scheme
+        // check it's not localhost
         $urlParts = parse_url($entityId ?? '');
-        if ($urlParts['host'] === 'localhost' || $urlParts['scheme'] === 'http') {
-            $this->errors[] = _t(
-                RealMeSetupTask::class . '.ERR_CONFIG_ENTITYID',
-                'The Entity ID (\'{entityId}\') must be https, not be \'localhost\', and must contain a valid ' .
-                    'service name and privacy realm e.g. https://my-realme-integration.govt.nz/p-realm/s-name',
-                array(
-                    'entityId' => $entityId
-                )
-            );
-
+        if ($urlParts['host'] === 'localhost') {
+            $this->errors[] = $validationMessage;
             // if there's this much wrong, we want them to fix it first.
             return;
         }
 
         $path = ltrim($urlParts['path'] ?? '');
-        $urlParts = preg_split("/\\//", $path ?? '');
-
+        $pathParts = preg_split("/\\//", $path ?? '');
 
         // A valid Entity ID is in the form of "https://www.domain.govt.nz/<privacy-realm>/<service-name>"
         // Validate Service Name
-        $serviceName = array_pop($urlParts);
+        $serviceName = array_pop($pathParts);
         if (mb_strlen($serviceName ?? '') > 20 || 0 === mb_strlen($serviceName ?? '')) {
             $this->errors[] = _t(
                 RealMeSetupTask::class . '.ERR_CONFIG_ENTITYID_SERVICE_NAME',
@@ -328,7 +319,7 @@ private function validateEntityID($forEnv)
         }
 
         // Validate Privacy Realm
-        $privacyRealm = array_pop($urlParts);
+        $privacyRealm = array_pop($pathParts);
         if (null === $privacyRealm || 0 === mb_strlen($privacyRealm ?? '')) {
             $this->errors[] = _t(
                 RealMeSetupTask::class . '.ERR_CONFIG_ENTITYID_PRIVACY_REALM',